Poly(sodium acrylamidomethyl propane sulfonate) P(NaAMPS), hydrolyzed polyacrylamide, and poly(vinylpyrrolidone) and copolymers thereof are water soluble polymers that have been previously disclosed in the literature and have found application in the viscosification of aqueous solutions which is achieved through a combination of high molecular weight and chain expansion due to repulsion of pendant ionic groups along the polymer chain or H-bonding. These polymers are salt-sensitive, thereby limiting their application in highly saline systems.
The betaines are a special class of zwitterions. These materials are self neutralized and contain no counterions. Moreover, the positive and negative charges are separated by alkyl groups.
Carboxymethacrylate betaine monomers (I) and polymers (II) are well-known and disclosed in U.S. Pat. No. 2,777,872 (Jan. 15, 1957), U.S. Pat. No. 2,834,758 (May 13, 1958) and U.S. Pat. No. 2,846,417 (Aug. 5, 1958). ##STR2##
Carboxyvinylpyridine betaine monomers and homopolymers (III) have also been reported [H. Ladenheim and H. Morawetz, J. Poly. Sci. 26, 251 (1957)]. ##STR3##
Sulfovinylpyridine betaine monomers and homopolymers (IV) are known [R. Hart and D. Timmerman, J. Poly. Sci. 28, 118 (1958)] and Ger. Auslegeschrift No. 1,207,630 and Galin, et al., Polymer 25, 121,254 (1984). ##STR4##
The butylsulfobetaine of poly(2-vinylpyridine) is soluble in water, but the butylsulfobetaine of poly(4-vinylypyridine) is not. Both betaines are soluble in salt solution.
Methacrylate based sulfobetaine monomers and homopolymers (V) are described by Galin Polymer 25, 121,254 (1984) and Ger. Auslegeshrift No. 1,207,630. ##STR5##
More recently, reports of vinylimidazolium sulfobetaine homopolymers (VI) have appeared [J. C. Salamone, et al Polymer 18, 1058 (1977); Polymer 19, 1157 (1978)]. ##STR6##
These homopolymers are insoluble in water, but soluble in certain salt solutions. In contrast to normal polyelectrolytes, the reduced viscosity of the soluble imidazolium sulfobetaine polymers increase with increasing salt concentration.